Lubricating oil



Patented Apr. 11, 1939 STATES PATNT mmmcs'rme on.

Clarence M. Loane, Hammond, Ind., assignor to Standard Oil Company,Chicago, 111., a corporation of Indiana No Drawing.

3 Claims.

This invention relates to lubricants and, in particular, to additionagents imparting improved properties to lubricants.

This invention has particular utility in improving the lubricatingproperties of lubricating oils and/or in preventing or inhibiting thecorrosion of hard metal alloy bearings such as copperlead,cadmium-nickel and cadmium-silver bearings which, to a large ,extent,have replaced soft metal bearings, such as Babbitt metal, in the trendtoward internal combustion engines having high compression ratios andincreased acceleration and increased speed characteristics. The use ofthe hard metal bearings has created lubricating and corrosion problems,particularly in connection with highly refined oils, some of which maybe very corrosive to bearings 01 the hard metal type.

As used herein highly refined lubricating 011 means viscous oils whichhave a minimum viscosity of S. A. E. 10 oils, or higher, and which havebeen subjected to such refining processes that the paraffinicity of theoil is markedly increased. It has been found that highly refined"lubricating oils cause corrosion to alloy bearings of the hard metaltype such as cadmium-silver alloy bearings to the extent of about 5mg/cm. and even greater when such bearings are submerged for 25 hours orless in an air agitated oil alloy bearings of the cadmium-silver type inthe presence of highly refined lubricating oils can be inhibited byadding to the said oil up to 2%, but preferably 0.05% to 0.75% ofcertain organic compounds, particularly the bivalent radical substitutedfive membered ring compounds having sulfur and nitrogen in the ring,said compounds having the general formula in which x is a benzo radicalor arylene derivative thereof and in which R is hydrogen or alkyl oraryl or SH or S alkyl or S aryl or Application November 27, 19136 SerialNo. 112,993

or- NH2 or NH alkyl or -N- alkyl or mixtures thereof and/or R1 may behydrogen or alkyl or halogen or amino or mercapto or alkyl substitutedamino or substituted mercapto or substituted'benzothiazole group orgroups and/or mixtures thereof.

Specific examples of the benzothiazoles having the general formula (6)in which R is hydrogen or alkyl or aryl or --SH or S alkylor -.--S--aryl or S-Calkyl And the naphthothiazole derivatives of the a above suchas:

Mercapto naphthothiazole Amino naphthothiazole Hexyl naphthothiazolePhenyl naphthothiazole In addition to the above compounds I have foundthat the benzo derivatives of the thio (AA) diazoles which are known asthe piazothioles are effective corrosion inhibitors.

The effectiveness of compounds or the above type as corrosion inhibitorsis demonstrated by merged in the air agitated oil at about 340 F.

the following test in which oils to which the inhibitor has been addedwere subjected to conditions which are more severe than thoseencountered in the actual operation of internal combustion engines.

Weighed cadmium-silver alloy bearings were submerged in samples of ahighly refined oil with and without the addition of the compound to betested and the oil air agitated while maintained at a temperature ofabout 341 F. At regular intervals the cadmium-silver alloy bearings wereremoved from the bath, washed free of oil, and weighed to determine theloss in Weight. The hearings were then replaced in the oil and furthertested. The oil used was a motor oil refined to such an extent that aloss in weight of more than 5 mg/cm. is obtained in hours or less on acadmium-silver alloy bearing subwhich oil has been preoxidized for 25 to50 hours 7 at about 340 F.

Control v Confrol+.2% mercapto-benzothiazo e The following results wereobtained on cadmium-silver alloy bearings when tested in the foregoingmanner,

Duration of test Oil 25 hrs. hrs. hrs.

Loss in weight (mg/cmfi) The above data definitely show the highinhibiting efiect of the mercapto benzothiazole.

Although I prefer to use the compounds of the hereinabove type which arecompletely oil soluble, equally effective results are obtained witharcane? highly refined lubricating oils normally corrosive to saidbearing metal alloys in internal combustion engines which comprisesadding to said lubricating oils a mercapto benzothiazole in a small butsufiicient quantity to effect the retardation of said corrosion to saidbearing metal alloys.

2. The method of-preventing corrosion of hard metal alloy bearings inthe presence of highly refined lubricating oils normally corrosive tosaid hard metal alloy bearings in internal combustion engines whichcomprises adding to said lubricating oils a bivalent radical substitutedfive-membered ring compound having sulfur and nitrogen in the ring andhaving the general formula in which X is a radical selected from thegroup consisting of a benzo radical and an arylene de rivative of abenzo radical, R is a substituent refined'lubricating oils normallycorrosive to said hard metal alloy bearings in internal combustionengines which comprises adding to said lubricating oils abenzothia zolehaving the general formula A Q N R1 C-R J s l in which R is asubstituent selected from the group consisting of hydrogen, an alkylradical and an .aryl radical, and R1 is a substituent selected from thegroup consisting of hydrogen, an alkyl radical, an aryl radical, amercapto group and an amino group, said benzothiazole being added tosaid lubricating oil in a small but sufiicient quantity to efiectivelyinhibit the corrosion of said hard metal alloy bearings.

CLARENCE M. LOANE.

